The present invention relates to capacitive transducers that directly and differentially sense force, pressure, strain, vibration, acceleration, gravity, sound, mechanical displacement, electric charge, radiation, and fluid flow over a wide dynamic range. More specifically, this invention relates to a method to fabricate capacitive transducers with one or more of variable-area capacitor elements.
Many potential high-volume applications exist for variable-area capacitors of U.S. Pat. No. 6,151,967 that have a high quiescent capacitance and a large change of capacitive compared to existent variable-gap capacitors. Accordingly, a method was developed to fabricate variable-area capacitors with flexible sensing diaphragms from materials having a wide range of modulus of elasticity.
Variable-area capacitive transducers have been constructed by bonding silicon diaphragms and membranes to glass substrates with metal film counter-electrodes. Capacitive transducers also have been constructed by bonding highly flexible metallized polymer films to polymer substrates. Both crystalline and polymer membranes with deposited metal films have been bonded to substrates with multiple electrodes to form capacitive transducers with multiple variable-area capacitor elements. All the forgoing embodiments of a variable-area capacitor transducer have been constructed by the method of the present invention.
One object of the present invention is to provide a common method to easily manufacture variable-area capacitive transducers of simple construction to transduce physical effects both directly and differentially.
A further object of the present invention is to provide a method to fabricate variable-area capacitors with sensing diaphragms of highly elastic materials such as single crystal silicon.
Another object of the present invention is to provide a method to fabricate variable-area capacitors from low-cost, thermoplastic materials such a polycarbonate.
Still another object of the present invention is to fabricate capacitive transducers with a plurality of variable-area capacitor elements.